A prospective study of possibly remediable psychotic and behavioral symptomatology in community-residing Alzheimer's disease (AD) patients will be conducted. These symptoms, which include agitation, suspiciousness, and delusional ideation, are a major cause of burden for AD caregivers and are a frequent reason for institutionalization. Although physicians are regularly called upon to treat these symptoms, limited information is available with respect to the specific nature, course and pharmacologic treatment of these symptoms. The objective of this study is to systematically evaluate and provide more definitive information on the nature, course, and treatment of these symptoms. This proposal has a longitudinal study protocol and a pharmacologic treatment protocol. A cohort of 150 subjects with AD will be assessed at 6-month intervals for 3 years; the presence or absence of specific psychotic and behavioral symptoms will be systematically evaluated. Patients who demonstrate significant behavioral symptoms will be eligible to enter a pharmacologic treatment protocol. This protocol will systematically evaluate the remediation of psychotic and behavioral symptoms in community-residing outpatients with AD, using two frequently prescribed antipsychotics (Haloperidol and Thioridazine) and one frequently prescribed antidepressant (Nortriptyline). The pharmacologic treatment protocol includes a 16-week double-blind placebo-controlled protocol and an open label maintenance protocol. Specifically, in a double-blind, parallel group design, AD patients (N = 124) with psychotic symptoms will be randomly assigned to one of four treatment groups receiving thioridazine, haloperidol, nortriptyline, or matched placebo tablets. Patients will be evaluated weekly for 16 weeks; dosage will be adjusted based on behavioral symptoms as well as side effects. Patients who complete the double-blind protocol will be treated in an open label study and seen for monthly dosage adjustments. Information will be obtained regarding efficacy, dosage, and side effects of treatment. The proposed study will provide more definitive information about the incidence, nature, and treatment course of psychotic behavioral symptoms in AD patients. The results should have direct relevance for physicians' prescribing patterns in non-institutionalized settings. The ultimate goal is to decrease the burden of AD on the caregiver.